-- This file is forked from https://github.com/rxi/json.lua

-- Copyright (c) 2020 rxi
--
-- Permission is hereby granted, free of charge, to any person obtaining a copy of
-- this software and associated documentation files (the "Software"), to deal in
-- the Software without restriction, including without limitation the rights to
-- use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
-- of the Software, and to permit persons to whom the Software is furnished to do
-- so, subject to the following conditions:
--
-- The above copyright notice and this permission notice shall be included in all
-- copies or substantial portions of the Software.
--
-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-- SOFTWARE.

if not __JSON_LUA__ then
    __JSON_LUA__ = true
    local __version__ = "1.5.2"

    Include("Version.lua")
    Version:set("JSON", __version__)
    ---@class JSON
    JSON = {}

    -------------------------------------------------------------------------------
    -- Encode
    -------------------------------------------------------------------------------

    local encode

    local escape_char_map = {
        ["\\"] = "\\",
        ['"'] = '"',
        ["\b"] = "b",
        ["\f"] = "f",
        ["\n"] = "n",
        ["\r"] = "r",
        ["\t"] = "t",
    }

    local escape_char_map_inv = { ["/"] = "/" }
    for k, v in pairs(escape_char_map) do
        escape_char_map_inv[v] = k
    end

    local function escape_char(c)
        return "\\" .. (escape_char_map[c] or string.format("u%04x", c:byte()))
    end

    local function encode_nil(val)
        return "null"
    end

    local function encode_table(val, stack)
        local res = {}
        stack = stack or {}

        -- Circular reference?
        if stack[val] then
            error("circular reference")
        end

        stack[val] = true

        if rawget(val, 1) ~= nil or next(val) == nil then
            -- Treat as array -- check keys are valid and it is not sparse
            local n = 0
            for k in pairs(val) do
                if type(k) ~= "number" then
                    error("invalid table: mixed or invalid key types")
                end
                n = n + 1
            end
            if n ~= #val then
                error("invalid table: sparse array")
            end
            -- Encode
            for i, v in ipairs(val) do
                table.insert(res, encode(v, stack))
            end
            stack[val] = nil
            return "[" .. table.concat(res, ",") .. "]"
        else
            -- Treat as an object
            for k, v in pairs(val) do
                if type(k) ~= "string" then
                    error("invalid table: mixed or invalid key types")
                end
                table.insert(res, encode(k, stack) .. ":" .. encode(v, stack))
            end
            stack[val] = nil
            return "{" .. table.concat(res, ",") .. "}"
        end
    end

    local function encode_string(val)
        return '"' .. val:gsub('[%z\1-\31\\"]', escape_char) .. '"'
    end

    local function encode_number(val)
        -- Check for NaN, -inf and inf
        if val ~= val or val <= -math.huge or val >= math.huge then
            error("unexpected number value '" .. tostring(val) .. "'")
        end
        return string.format("%.14g", val)
    end

    local type_func_map = {
        ["nil"] = encode_nil,
        ["table"] = encode_table,
        ["string"] = encode_string,
        ["number"] = encode_number,
        ["boolean"] = tostring,
    }

    encode = function(val, stack)
        local t = type(val)
        local f = type_func_map[t]
        if f then
            return f(val, stack)
        end
        error("unexpected type '" .. t .. "'")
    end

    ---将 Lua 对象编码为 JSON 字符串。
    ---@param val any
    ---@return string
    function JSON.encode(val)
        return (encode(val))
    end

    -------------------------------------------------------------------------------
    -- Decode
    -------------------------------------------------------------------------------

    local parse

    local function create_set(...)
        local res = {}
        for i = 1, select("#", ...) do
            res[select(i, ...)] = true
        end
        return res
    end

    local space_chars = create_set(" ", "\t", "\r", "\n")
    local delim_chars = create_set(" ", "\t", "\r", "\n", "]", "}", ",")
    local escape_chars = create_set("\\", "/", '"', "b", "f", "n", "r", "t", "u")
    local literals = create_set("true", "false", "null")

    local literal_map = {
        ["true"] = true,
        ["false"] = false,
        ["null"] = nil,
    }

    local function next_char(str, idx, set, negate)
        for i = idx, #str do
            if set[str:sub(i, i)] ~= negate then
                return i
            end
        end
        return #str + 1
    end

    local function decode_error(str, idx, msg)
        local line_count = 1
        local col_count = 1
        for i = 1, idx - 1 do
            col_count = col_count + 1
            if str:sub(i, i) == "\n" then
                line_count = line_count + 1
                col_count = 1
            end
        end
        error(string.format("%s at line %d col %d", msg, line_count, col_count))
    end

    local function codepoint_to_utf8(n)
        -- http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=iws-appendixa
        local f = math.floor
        if n <= 0x7f then
            return string.char(n)
        elseif n <= 0x7ff then
            return string.char(f(n / 64) + 192, n % 64 + 128)
        elseif n <= 0xffff then
            return string.char(f(n / 4096) + 224, f(n % 4096 / 64) + 128, n % 64 + 128)
        elseif n <= 0x10ffff then
            return string.char(f(n / 262144) + 240, f(n % 262144 / 4096) + 128, f(n % 4096 / 64) + 128, n % 64 + 128)
        end
        error(string.format("invalid unicode codepoint '%x'", n))
    end

    local function parse_unicode_escape(s)
        local n1 = tonumber(s:sub(1, 4), 16)
        local n2 = tonumber(s:sub(7, 10), 16)
        -- Surrogate pair?
        if n2 then
            return codepoint_to_utf8((n1 - 0xd800) * 0x400 + (n2 - 0xdc00) + 0x10000)
        else
            return codepoint_to_utf8(n1)
        end
    end

    local function parse_string(str, i)
        local res = ""
        local j = i + 1
        local k = j

        while j <= #str do
            local x = str:byte(j)

            if x < 32 then
                decode_error(str, j, "control character in string")
            elseif x == 92 then -- `\`: Escape
                res = res .. str:sub(k, j - 1)
                j = j + 1
                local c = str:sub(j, j)
                if c == "u" then
                    local hex = str:match("^[dD][89aAbB]%x%x\\u%x%x%x%x", j + 1)
                        or str:match("^%x%x%x%x", j + 1)
                        or decode_error(str, j - 1, "invalid unicode escape in string")
                    res = res .. parse_unicode_escape(hex)
                    j = j + #hex
                else
                    if not escape_chars[c] then
                        decode_error(str, j - 1, "invalid escape char '" .. c .. "' in string")
                    end
                    res = res .. escape_char_map_inv[c]
                end
                k = j + 1
            elseif x == 34 then -- `"`: End of string
                res = res .. str:sub(k, j - 1)
                return res, j + 1
            end

            j = j + 1
        end

        decode_error(str, i, "expected closing quote for string")
    end

    local function parse_number(str, i)
        local x = next_char(str, i, delim_chars)
        local s = str:sub(i, x - 1)
        local n = tonumber(s)
        if not n then
            decode_error(str, i, "invalid number '" .. s .. "'")
        end
        return n, x
    end

    local function parse_literal(str, i)
        local x = next_char(str, i, delim_chars)
        local word = str:sub(i, x - 1)
        if not literals[word] then
            decode_error(str, i, "invalid literal '" .. word .. "'")
        end
        return literal_map[word], x
    end

    local function parse_array(str, i)
        local res = {}
        local n = 1
        i = i + 1
        while 1 do
            local x
            i = next_char(str, i, space_chars, true)
            -- Empty / end of array?
            if str:sub(i, i) == "]" then
                i = i + 1
                break
            end
            -- Read token
            x, i = parse(str, i)
            res[n] = x
            n = n + 1
            -- Next token
            i = next_char(str, i, space_chars, true)
            local chr = str:sub(i, i)
            i = i + 1
            if chr == "]" then
                break
            end
            if chr ~= "," then
                decode_error(str, i, "expected ']' or ','")
            end
        end
        return res, i
    end

    local function parse_object(str, i)
        local res = {}
        i = i + 1
        while 1 do
            local key, val
            i = next_char(str, i, space_chars, true)
            -- Empty / end of object?
            if str:sub(i, i) == "}" then
                i = i + 1
                break
            end
            -- Read key
            if str:sub(i, i) ~= '"' then
                decode_error(str, i, "expected string for key")
            end
            key, i = parse(str, i)
            -- Read ':' delimiter
            i = next_char(str, i, space_chars, true)
            if str:sub(i, i) ~= ":" then
                decode_error(str, i, "expected ':' after key")
            end
            i = next_char(str, i + 1, space_chars, true)
            -- Read value
            val, i = parse(str, i)
            -- Set
            res[key] = val
            -- Next token
            i = next_char(str, i, space_chars, true)
            local chr = str:sub(i, i)
            i = i + 1
            if chr == "}" then
                break
            end
            if chr ~= "," then
                decode_error(str, i, "expected '}' or ','")
            end
        end
        return res, i
    end

    local char_func_map = {
        ['"'] = parse_string,
        ["0"] = parse_number,
        ["1"] = parse_number,
        ["2"] = parse_number,
        ["3"] = parse_number,
        ["4"] = parse_number,
        ["5"] = parse_number,
        ["6"] = parse_number,
        ["7"] = parse_number,
        ["8"] = parse_number,
        ["9"] = parse_number,
        ["-"] = parse_number,
        ["t"] = parse_literal,
        ["f"] = parse_literal,
        ["n"] = parse_literal,
        ["["] = parse_array,
        ["{"] = parse_object,
    }

    parse = function(str, idx)
        local chr = str:sub(idx, idx)
        local f = char_func_map[chr]
        if f then
            return f(str, idx)
        end
        decode_error(str, idx, "unexpected character '" .. chr .. "'")
    end

    ---将 JSON 字符串解码为 Lua 对象。
    ---@param str string
    ---@return any
    function JSON.decode(str)
        if type(str) ~= "string" then
            error("expected argument of type string, got " .. type(str))
        end
        local res, idx = parse(str, next_char(str, 1, space_chars, true))
        idx = next_char(str, idx, space_chars, true)
        if idx <= #str then
            decode_error(str, idx, "trailing garbage")
        end
        return res
    end
end -- __JSON_LUA__
